På BillerudKorsnäs produktionsanläggning i Gävle tillverkas vätskekartong och kraftliner. I produktionsprocessen sållas träflisen i anläggningens två flissållar, såll-1 och såll-2. Såll-1 har under många år haft problem med tillgängligheten på grund av skador på vitala skruvförband och sprickbildning i anslutning till svetsar. Denna rapport syftar till att öka tillgängligheten för såll-1, med målet att identifiera orsaker till varför sållet havererar och därefter presentera åtgärder för att förlänga livslängden på skruvar och minska sprickbildning.  Metoderna som använts under arbetet är en inledande datainsamling för att tillförskaffa den nödvändiga bakgrundsinformationen. Därefter har teori kring svets- och skruvförband bearbetats för att förstå generella konstruktionsprinciper för de nämnda områdena. För att kunna applicera teorierna i det verkliga fallet har en maskinbesiktning varit nödvändig för att identifiera brister i konstruktionen. Då såll2 inte har samma typ av tillgänglighetsproblem har en maskinjämförelse av de två sållen utförts.  Arbetet har resulterat i att konstruktionsprincipiella brister identifierats i de problemdrabbade skruvförbanden som sammanfogar konstruktionen. Korta klämlängder och färgskikt i kontaktytor i vissa av skruvförbanden kan göra att rätt kontakttryck inte uppnås. Beroende på vilka friktionsförhållande som råder i gängan och under skruvskallen resulterar åtdragningsmomentet i att olika förspänningar uppstår i skruven. Detta leder i vissa fall till att tillräcklig förspänning av skruven inte uppnås. I anslutning till de svetsar där sprickor uppstår, identifieras ogynnsamma dimensionsövergångar där spänningskoncentrationer kan uppstå. Dessa brister tillsammans med en misstänkt överbelastning på grund av spånansamlingar som adderar extra vikt till konstruktionen bedöms vara de bakomliggande orsakerna till den frekventa skadehistoriken och därmed den undermåliga tillgängligheten.  Åtgärderna som bedöms kunna öka tillgängligheten är att öka klämlängden i skruvförbanden, konstruera alla skruvförband utan färgskikt i dess kontaktytor. Reducera risken för överbelastning genom att undvika spånansamlingar i konstruktionen. Möjliggör jämnare produktion och därmed jämnare belastning mellan såll-1 och såll-2. Konstruera utan plötsliga dimensionsövergångar och speciellt i anslutning till svetsar. / At the production site in Gävle, Sweden, BillerudKorsnäs produces liquid carton for packaging food and beverages and liners used in cardboard boxes. For this manufacturing process pulp is used that is extracted from wood chips. In the production process the wood chips are separated in two different sieves, Sieve 1 and Sieve 2. During several years, Sieve 1 has had a record of failures of bolted joints and cracks in welded components. The aim of this investigation is to increase the production availability of Sieve 1, with the goal to identify the causes behind the frequent failure record, and then present actions to increase the life span of the mentioned components.  The methods used in this investigation is initially consisting of collecting data in order to get the basic knowledge and understanding of the sieve and its problems. Thereafter the theory that involves the use of bolted joints and welds to understand general construction principles about the mentioned areas. To be able to apply these theories an inspection of sieve 1, has been necessary to identify constructional shortcomings. The other sieve, Sieve 2, has not had the same failure record. Therefore the differences between the two sieves has been evaluated.  The methods has resulted in the identification of some shortcomings regarding the bolted joints and its clamping lengths, and the paint coating that the whole construction is covered with. Another aspect is the friction in the contact areas of the bolt threads and under the bolt head, which in some cases may lead to that the applied torque does not give enough pretension to the bolt.  Adjacent to the welds where cracks occur, unfavorable dimensional transitions are detected where stress concentrations can occur. These flaws along with a suspected overload due to chip masses that add extra weight to the construction are considered to be the underlying causes of the frequent damage history and thus the inferior availability.  The measures estimated to increase accessibility are to increase the clamping length in screw joints, design all screw joints without any paint layer in its contact surfaces. Reduce the risk of overload by avoiding chip masses in the construction. Enable a more even production between the sieves. Design without sudden dimensional transitions.

Human - Technology - Organization (HTO) is a well-established, general unifying concept in the Swedish Accident Investigation Authority (SHK) that represents an approach, knowledge and use of various tools regarding interactions between people, technology and organizational factors. The HTO-perspective is well described in literature but there are few studies on how SHKs staff experiences working according to this method in their investigations. The aim of this study was therefore to describe their HTO-perspective, examine how it is used in the investigations at SHK and describe the investigators experience of working with the HTO-perspective as well as the method's usefulness compared to old methods in accident investigations. A literature study has been conducted in the areas of HTO, Theory of planned behavior (TPB) and safety culture. TPB and safety culture are described in this paper since they highlight the different aspects of a HTO-perspective. The hypothesis was answered by using semi-structured interviews. The interviews were analyzed by a content analysis and themes were identified. Furthermore the material from the interviews was subsequently structured through a Strength – Weakness – Opportunities – Threats analysis (SWOT), i.e. the informants' view on the HTO-perspective was structured based on the strengths, weaknesses, opportunities and threats SHKs staff experience that the method has in the investigative work. The informants consisted of two investigators at SHK who 3have worked with accident investigations for a long time in various roles. The results yielded that the investigators had a positive attitude towards conducting investigations according to the HTO-perspective because they feel that this perspective provides them with cross-competence. A flaw is though that the perspective lacks a structured approach. As a result of this, the investigators own experiences and expertise play a major role in the quality of the investigation. As the study's aim is met and the informants are considered to be experts the validity requirements are also fulfilled.